DOCSLIB.ORG

University of Nevada, Reno Patterns of Lithology, Structure, Alteration

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
University of Nevada, Reno Patterns of Lithology, Structure, Alteration University of Nevada, Reno Patterns of Lithology, Structure, Alteration, Trace Elements, Carbonate Mineralogy, and Stable Isotopes around High-Grade Carlin-type Gold Deposits: Turquoise Ridge Deposit, Getchell District, Nevada A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Geology by Michael D. Cassinerio Dr. John Muntean/Thesis Advisor May, 2010 © by Michael Cassinerio All Rights Reserved i Abstract Few data sets have been published that depict the extent of hydrothermal features surrounding high-grade ore bodies in Carlin-type gold deposits (CTGDs) in Nevada, making exploration, development, and production difficult, especially where visually unaltered, unmineralized rocks occur in close proximity to ore. This thesis, which is divided into 3 standalone chapters, investigates several hydrothermal features associated with the high-grade Turquoise Ridge CTGD in the Getchell District. Traditional exploration tools such as patterns of lithology, structure, visible hydrothermal alteration, trace elements, and clay mineralogy are presented in Chapter 1 to test for the presence of haloes that can potentially be used as vectoring tools in honing in on high-grade ore zones at the Turquoise Ridge CTGD. Carbonate staining was utilized to determine differences in carbonate mineralogy associated with more reactive and non-reactive carbonate host-rocks (Chapter 2). Stable isotopes (δ18O and δ13C) are presented in Chapter 3 to test for the presence of potentially more pervasive cryptic alteration haloes relative to visible hydrothermal alteration and trace element anomalies. Closely-spaced diamond drill holes along two cross-sections across the High Grade Bullion (HGB) ore zone at the north end of Turquoise Ridge were logged in detail. The logging information, gold assays, multi-element analyses, and spectral reflectance analyses were plotted on a 1:600 scale cross-section, from which controls on gold (Au) grade and haloes to ore zones were interpreted. The Eocene-age Turquoise Ridge CTGD is hosted within a complexly deformed package of Cambrian-Ordovician sedimentary and volcanic rocks that is characterized by ii rapid facies changes and soft-sediment deformation. The lowermost unit comprises variably calcareous, carbonaceous mudstones and limestones that are overlain by a series of sedimentary debris flow breccias. Above the breccias are deformed tuffaceous mudstones and limestones, which inter-finger to the northeast with a thick sequence of pillow basalt. Both the sedimentary debris flow breccias and the basalt pinch out to the south, and are interpreted to be controlled by a Cambrian-Ordovician, west-northwest trending, northeast-facing, basin margin. Further up section the rocks are mainly mudstone, basalt, and chert. The rocks are intruded by Cretaceous dacite porphyry dikes. The Turquoise Ridge deposit occurs in the hanging wall of the east-dipping, north-northwest-striking Getchell fault zone, which is the main fault in the district. Much of the HGB ore zone occurs along complex intersections between steep, small-displacement faults, folds, and fractured calcareous lithologies, especially within the series of sedimentary breccias. The Au grades commonly show abrupt variations, locally changing from ≥17 ppm to <0.34 ppm within a few meters. Zones of ≥0.34 ppm Au extend up to 120 meters above and up to 150 meters below the HGB; occur within the Getchell fault; and occur along several steep, small-displacement, antithetic faults in the hanging wall of the Getchell fault. Visible alteration, consisting of decalcification, argillization, and silicification, strongly correlates with Au grades of >0.34 ppm. Correlation matrices and factor analysis of downhole multi-element data show Au is strongly associated with Hg, As, W, S, Tl, Sb, and Te, but has a strong negative correlation with Ca, Mg, and Sr that is consistent with decalcification being the main alteration type. Values of ≥100 ppm As form a halo up to 30 m beyond the 0.34 ppm Au iii contour and visible alteration, whereas the 5 ppm Sb contour forms a halo up to 12 m wide. With the possible exception of Hg, other features derived from the multi-element data, including Tl, Te, degree of sulfidation (DOS), Au factor scores (derived from factor analysis), and Ca (to monitor decalcification) do not form significant, coherent haloes to the 0.34 ppm Au contour or visible alteration. Kaolinite and illite commonly occur in zones of ≥0.34 ppm Au. Inspection of samples from ore zones using an SEM show they are intimately intergrown with arsenian pyrite. Kaolinite- and illite-bearing fractures surfaces form incoherent haloes extending up to 20 m beyond visible alteration in otherwise unaltered rocks. Limited analyses of these fractures using a Niton handheld XRF show the fractures can contain significantly higher As than the adjacent wall rock. Carbonate staining was utilized to determine the spatial distribution of carbonate mineralogy relative to high-grade gold ore at the Turquoise Ridge Carlin-type gold deposit. Specifically, dilute hydrochloric acid containing both alizarin red S and potassium ferricyanide was utilized to differentiate between calcite, ferroan calcite, ferroan dolomite and dolomite in the Cambrian-Ordovician carbonate host rocks at Turquoise Ridge. Detailed carbonate staining was conducted on 31 drill holes throughout the north end of Turquoise Ridge. Results reveal a distinct spatial relationship between gold mineralization, ferroan calcite, and the southern margin of a thick basalt within the Cambrian-Ordovician stratigraphic package that is referred to as the northern pillow basalt (NPB). High-grade gold ore (≥17 ppm Au) within the HGB ore zone occurs exclusively within ferroan calcite-bearing host rocks. The transition from iv ferroan calcite to calcite with depth occurs at the base of the HGB ore zone. Non- ferroan calcite is distal to the NPB, both laterally and with depth. A close spatial association between the distribution of ferroan calcite and the NPB suggests iron was likely liberated from the basalt during seawater alteration of the basalts, and/or the emplacement of the Cretaceous intrusions and was mobilized into adjacent limestones, forming ideal host rocks for subsequent gold mineralization. Acidic, sulfur-rich, auriferous hydrothermal fluids dissolved ferroan carbonates, which liberated iron. Aqueous sulfide in the fluid reacted with the iron, which destabilized aqueous gold-sulfide complexes, resulting in the formation of auriferous pyrite and marcasite. The presence of interlayered basalts and ferroan carbonates could be important exploration criteria in the identification of future target areas in the Getchell District and throughout Nevada. Furthermore and most importantly, careful carbonate staining should be routinely employed, given that it provides inexpensive, real-time data. Analyses of carbonates from both visibly altered and unaltered rocks at Turquoise Ridge yielded δ18O values from 13.5‰ to 21.6‰ and δ13C values from -8.2‰ to 1.2‰. Most of the δ18O values associated with visibly unaltered recrystallized micrite are between 17.6‰ and 19.0‰, well below typical δ18O values associated with unaltered Paleozoic carbonates (22‰ to 28‰). The spatial distribution of δ18O values along an east-west cross-section through the northern portion of the Turquoise Ridge deposit reveal the lowest δ18O and δ13C values occur within visibly altered wall rocks associated with ore zones and defined fluid pathways. Stable isotopic alteration haloes v are limited to visible alteration and do not extend beyond hydrothermal alteration into adjacent unaltered wallrocks. Similarly, elevated trace element concentrations (e.g., Au, As, Hg, Te, Sb,and Tl) are largely limited to visibly altered wall rocks, with elevated concentrations associated with bleached clay/calcite-lined fractures extending beyond continuous hydrothermal alteration in otherwise visibly unaltered wall rocks. The lack of wide, coherent haloes of various hydrothermal features surrounding ore at Turquoise Ridge is suggestive of a restrictive, fracture-controlled fluid flow network, rather than large-scale, pervasive, lithologically-controlled fluid flow. Ore fluids likely ascended along the pre-existing Getchell fault zone and into the steep, small-displacement, antithetic faults in the hanging wall and the main dacite porphyry dike before encountering highly fractured, reactive carbonate-bearing lithologies, especially the sedimentary breccias and deformed mudstones and limestones adjacent to the basalt. Increased surface area in these zones allowed more fluid:rock interaction, which resulted in more pervasive carbonate dissolution, sulfidation, and Au deposition in the HGB. A large zone <25% RQD values that surrounds ore supports exploitation of these pre-existing fracture networks and as well as fracturing caused by collapse during carbonate dissolution associated with ore formation. The results of this study show that few hydrothermal features extend beyond visible alteration (decalcification, argillization, and/or silcificiation) or low-grade gold assays. The features that do only form narrow, discontinuous haloes that are mostly restricted to fractures. None of the features investigated in this study, including visible alteration and low-grade gold assays, form pervasive haloes to ore on the scale of tens vi to hundreds of meters, suggesting widespread alteration haloes associated with CTGDs is a common misperception, especially high-grade
Load more

Recommended publications
  • SEDIMENT-HOSTED AU DEPOSITS (MODEL 26A; Berger, 1986) By
    SEDIMENT-HOSTED AU DEPOSITS (MODEL 26a; Berger, 1986) by Albert H. Hofstra, Joel S. Leventhal, David J. Grimes, and William D. Heran SUMMARY OF RELEVANT GEOLOGIC, GEOENVIRONMENTAL, AND GEOPHYSICAL INFORMATION Carlin-type deposits are epigenetic, large-tonnage, low-grade, sediment-hosted disseminated gold deposits. The deposits are known mainly in northern Nevada and northwestern Utah where they are arranged in clusters and belts. The deposits in this region are estimated to contain about 5,000 tonnes of gold, more than half of which (~3100 tonnes) is in the Carlin Trend. Approximately 1,000 tonnes of gold have been produced. Carlin-type gold deposits are one of the most important types currently being mined in the western United States. Many aspects of this geoenvironmental model also apply to distal disseminated deposits as defined by Cox and Singer (1990), Doebrich and Theodore (in press), and Howe and others (1995). Deposit geology Unoxidized refractory ore: Refractory ore consists of variably decalcified, dedolomitized, argillized, silicified, sulfidized, carbonaceous sedimentary rocks that contain disseminated iron, arsenic, antimony, mercury, and thallium sulfide minerals. Base-metal sulfide minerals are rare or absent in most deposits. Although pyrite, marcasite, orpiment, and realgar have high acid-generating capacity, they generally are present in small amounts (much less than 5 volume percent) and are usually disseminated in, or surrounded by, carbonate rocks with high acid-consuming capacity. Zones with 5-50 volume percent pyrite, marcasite, orpiment, or realgar are present in some deposits. Ore is refractory because much of the gold forms sub-micron grains in pyrite and marcasite and because carbon in the rock can extract gold from cyanide solutions.
    [Show full text]
  • Technical Report Getchell Project NI 43-101 Technical Report Premier Gold Mines Limited and I-80 Gold Corp
    AMC Mining Consultants (Canada) Ltd. BC0767129 200 Granville Street, Suite 202 Vancouver BC V6C 1S4 Canada T +1 604 669 0044 E [email protected] W amcconsultants.com Technical Report Getchell Project NI 43-101 Technical Report Premier Gold Mines Limited and i-80 Gold Corp Humboldt County, Nevada, USA In accordance with the requirements of National Instrument 43-101 “Standards of Disclosure for Mineral Projects” of the Canadian Securities Administrators Qualified Persons: D Nussipakynova, P.Geo. P Greenhill, FAusIMM (CP) AMC Project 720031 Effective date 23 July 2020 Report date 22 January 2021 Unearth a smarter way Getchell Project NI 43-101 Technical Report Premier Gold Mines Limited and i-80 Gold Corp 720031 1 Summary 1.1 Introduction This Technical Report (the Report) provides an update of the Mineral Resource estimates and metallurgy of the Mineral Resources identified within the Getchell Project (Property) located in Humboldt County, Nevada, USA. The Report has been prepared by AMC Mining Consultants (Canada) Ltd. (AMC) of Vancouver, Canada on behalf of Premier Gold Mines Limited / i-80 Gold Corp (i-80 or the Companies). On 10 August 2020, Premier entered into a definitive purchase agreement with affiliates of Waterton Global Resource Management, Inc. to acquire from Waterton all of the outstanding membership interests of Osgood Mining Company LLC (OMC). The Property comprises a number of property parcels which collectively encompass 2,545 acres in the Potosi mining district. The four-square miles of land contain all areas of past gold production and the area of the currently estimated Mineral Resource. This area includes the historical Pinson Mine.
    [Show full text]
  • Net Income Rises 29% to $514 Million ($0.59 Per Share) Expanded Margins Increase Profitability in Q1
    FIRST QUARTER REPORT - MAY 6, 2008 For a full explanation of results, the Financial Statements and Management Discussion & Analysis, Based on US GAAP and expressed in US dollars full-year guidance at significant mines, and mine statistics, please see the Company’s website, www.barrick.com. Net Income Rises 29% to $514 Million ($0.59 per share) Expanded Margins Increase Profitability in Q1 Highlights • The Company reported first quarter net income of $514 million ($0.59 per share) and operating cash flow of $728 million ($0.83 per share) compared to a net loss of $159 million ($0.18 per share) and operating cash flow of $163 million ($0.19 per share) in the prior year period. Reported net income rose 29% compared to prior year adjusted net income of $398 million ($0.46 per share)1 and included $29 million of post-tax special items that reduced income by $0.03 per share. Adjusting for these special items, earnings of $0.62 per share are a Company record. The realized gold price of $925 per ounce matched the average spot price for the quarter. • First quarter gold production was 1.74 million ounces at total cash costs of $393 per ounce2, and copper production was 87 million pounds at total cash costs of $0.94 per pound2. The Company maintains full year production guidance of 7.6 - 8.1 million ounces of gold at total cash costs of $390 - $415 per ounce and 380 - 400 million pounds of copper at total cash costs of $1.15 - $1.25 per pound.
    [Show full text]
  • Annual Information Form for the Year Ended December 31, 2018 Dated As of March 22, 2019 BARRICK GOLD CORPORATION
    Barrick Gold Corporation Brookfield Place, TD Canada Trust Tower Suite 3700, 161 Bay Street, P.O. Box 212 Toronto, ON M5J 2S1 Annual Information Form For the year ended December 31, 2018 Dated as of March 22, 2019 BARRICK GOLD CORPORATION ANNUAL INFORMATION FORM TABLE OF CONTENTS GLOSSARY OF TECHNICAL AND BUSINESS TERMS 4 REPORTING CURRENCY, FINANCIAL AND RESERVE INFORMATION 10 FORWARD-LOOKING INFORMATION 11 SCIENTIFIC AND TECHNICAL INFORMATION 14 THIRD PARTY DATA 15 GENERAL INFORMATION 15 Organizational Structure 15 Subsidiaries 16 Areas of Interest 18 General Development of the Business 18 History 18 Significant Acquisitions 18 Strategy 19 Recent Developments 21 Results of Operations in 2018 22 NARRATIVE DESCRIPTION OF THE BUSINESS 26 Production and Guidance 26 Reportable Operating Segments 26 Barrick Nevada 27 Pueblo Viejo (60% basis) 28 Lagunas Norte 29 Veladero (50% basis) 29 Turquoise Ridge (75% basis) 30 Acacia Mining plc (63.9% basis) 31 Pascua-Lama Project 32 Mineral Reserves and Mineral Resources 33 Marketing and Distribution 46 Employees and Labor Relations 47 Competition 48 Sustainability 48 Operations in Emerging Markets: Corporate Governance and Internal Controls 49 Board and Management Experience and Oversight 50 Communications 51 - i - Internal Controls and Cash Management Practices 51 Managing Cultural Differences 52 Books and Records 52 MATERIAL PROPERTIES 52 Cortez Property 52 Goldstrike Property 58 Turquoise Ridge Mine 63 Pueblo Viejo Mine 69 Veladero Mine 76 Kibali Mine 86 Loulo-Gounkoto Mine Complex 93 EXPLORATION
    [Show full text]
  • Carlin-Type Gold Deposits in Nevada: Critical Geologic Characteristics and Viable Models
    ©2005 Society of Economic Geologists, Inc. Economic Geology 100th Anniversary Volume pp. 451–484 Carlin-Type Gold Deposits in Nevada: Critical Geologic Characteristics and Viable Models JEAN S. CLINE,† University of Nevada, Las Vegas, 4505 Maryland Parkway, Box 454010, Las Vegas, Nevada 89154-4010 ALBERT H. HOFSTRA, Mineral Resources Program, U.S. Geological Survey, Mail Stop 973, Box 25046, Denver, Colorado 80225 JOHN L. MUNTEAN, Nevada Bureau of Mines and Geology, Mail Stop 178, University of Nevada, Reno, Nevada 89557-0088 RICHARD M. TOSDAL, AND KENNETH A. HICKEY Mineral Deposit Research Unit, University of British Columbia, 6339 Stores Road, Vancouver, British Columbia, Canada V6T 1Z4 Abstract Carlin-type Au deposits in Nevada have huge Au endowments that have made the state, and the United States, one of the leading Au producers in the world. Forty years of mining and numerous studies have pro- vided a detailed geologic picture of the deposits, yet a comprehensive and widely accepted genetic model re- mains elusive. The genesis of the deposits has been difficult to determine owing to difficulties in identifying and analyzing the fine-grained, volumetrically minor, and common ore and gangue minerals, and because of postore weathering and oxidation. In addition, other approximately contemporaneous precious metal deposits have overprinted, or are overprinted by, Carlin-type mineralization. Recent geochronological studies have led to a consensus that the Nevada deposits formed ~42 to 36 m.y. ago, and the deposits can now be evaluated in the context of their tectonic setting. Continental rifting and deposi- tion of a passive margin sequence followed by compressional orogenies established a premineral architecture of steeply dipping fluid conduits, shallow, low dipping “traps” and reactive calcareous host rocks.
    [Show full text]
  • Nevada Excellence in Mine Reclamation Awards 1991-2020
    Nevada Excellence in Mine Reclamation Awards 1991-2020 Year Company and Project Description Award Category Pg 1 of 3 2020 KGHM Robinson Mine – Lane City Waste Rock Legacy Waste Rock Reclamation Facility Reclamation Project 2020 Hudbay Minerals/Mason Resources (US) Inc. – Concurrent Exploration Reclamation Mason Exploration Project 2019 B2Gold Corp. – Rockland Exploration Drilling Exploration Project Reclamation Project 2019 Barrick Gold – Bullfrog Mine Partial Pit Backfill Pit Lake Remediation 2019 Nevada Gold Mines – Butte Canyon Historic WRF Legacy WRF Remediation and Closure Reclamation 2019 Newmont USA Limited – Buttes Exploration Project Abandoned Mines Hazard Mitigation Reclamation 2019 Paramount Gold Nevada Corp. – Sleeper Mine Pit Post-Mining Land Use Planning Lake Recreation Site 2019 Western Exploration LLC – Doby George Concurrent Exploration Reclamation Exploration Project 2018 Coeur Rochester, Inc. – Marzen House Museum Cooperative Partnership in Preservation of Exhibit on Rochester Mining District Mining History 2018 KGHM Robinson Mine – Reclamation through Leadership in Reclamation Mining 2018 Kinross Gold U.S.A., Inc. – Nevada Conservation Leadership in Conservation Planning Credit System Credit Transfer at Bald Mtn. Mine 2018 Lithium Nevada Corporation – Upper Basin Exploration Project Reclamation Exploration Project Reclamation 2018 Newmont USA Ltd. – North Area Leach Phase I-II Concurrent Reclamation Closure 2017 Comstock Mining, Inc. – Rebuilding of State Route Abandoned Mine Lands Hazard 342 and Reclamation of Historic
    [Show full text]
  • Using Pyrite to Track Evolving Fluid Pathways and Chemistry in Carlin-Type Deposits
    Using Pyrite to Track Evolving Fluid Pathways and Chemistry in Carlin-type Deposits Anthony A. Longo, Jean S. Cline Geoscience Department, University of Nevada Las Vegas, 4505 Maryland Parkway, Las Vegas, NV USA 89154-4010 John L. Muntean Nevada Bureau of Mines and Geology, University of Nevada Reno, Mailstop 178, Reno, NV, USA 89557-0088 Abstract. Submicron Au in Carlin-type deposits in use as fingerprints to identify the evolution of fluids and northern Nevada, USA, occurs in trace-element-rich pathways in time and space. Improving our pyrite, and zoning of the trace element signatures varies understanding of fluid pathways facilitates deposit- and across pyrite rims and vertically and laterally across district-scale exploration and contributes to deposit these deposits. These patterns reveal the chemical fluid-flux models. evolution and flux of ore fluids along individual fluid pathways and further indicate the relative timing of 2 Turquoise Ridge Deposit Geology permeable fluid pathways with respect to one another. Ore pyrite chemistry along one east-west transect at The Turquoise Ridge deposit, Getchell district northern Turquoise Ridge in the Getchell district demonstrates Nevada, is located in the hanging wall of the Getchell fluid ingress from the east dipping Getchell fault at fault (NNW strike, ~40-55°E dip), the primary ore- depth into the hanging wall, but also reveals that ore controlling structure in the district (Hotz and Wilden deposition migrated in an east to west direction toward 1964). Information from hundreds of closely spaced the Getchell fault over time. This east to west evolution underground diamond drill holes and surface holes was of permeability indicates transient opening and sealing used to prepare detailed 1:600 scale underground, east- of ore fluid pathways during mineralization and may west cross sections that illustrate lithologies, alteration, have been a response to changing strain domains related structure, and contoured Au grades.
    [Show full text]
  • Annual Information Form for the Year Ended December 31, 2017 Dated As of March 23, 2018
    Barrick Gold Corporation Brookfield Place, TD Canada Trust Tower Suite 3700, 161 Bay Street, P.O. Box 212 Toronto, ON M5J 2S1 Annual Information Form For the year ended December 31, 2017 Dated as of March 23, 2018 BARRICK GOLD CORPORATION ANNUAL INFORMATION FORM TABLE OF CONTENTS GLOSSARY OF TECHNICAL TERMS .................................................................................................. 4 REPORTING CURRENCY, FINANCIAL AND RESERVE INFORMATION ................................ 10 FORWARD-LOOKING INFORMATION ............................................................................................ 10 SCIENTIFIC AND TECHNICAL INFORMATION ............................................................................ 13 GENERAL INFORMATION .................................................................................................................. 13 Organizational Structure ................................................................................................................ 13 Subsidiaries .................................................................................................................................... 14 Areas of Interest ............................................................................................................................. 16 General Development of the Business ........................................................................................... 16 History .............................................................................................................................
    [Show full text]
  • Characterization of Mine Leachates and the Development of a Ground-Water Monitoring Strategy for Mine Sites EPA/600/R-99/007 February 1999
    United States Office of Research and EPA/600/R-99/007 Environmental Protection Development February 1999 Agency Washington, D.C. 20460 Characterization of Mine Leachates and the Development of a Ground-Water Monitoring Strategy for Mine Sites EPA/600/R-99/007 February 1999 Characterization of Mine Leachates and the Development of a Ground-Water Monitoring Strategy for Mine Sites by Russell H. Plumb, Jr. Lockheed Martin Services Group Las Vegas, Nevada Contract Number 68-C5-0091 Project Officer Larry A. Eccles National Environmental Research Laboratory U.S. Environmental Protection Agency Las Vegas, Nevada Notice Although the research described in this report was supported by the U.S. Environmental Protection Agency, through its Office of Research and Development, it has not been subjected to Agency policy review and therefore does not necessarily reflect the views of the Agency. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. ii Acknowledgment This work was conducted under Work Assignments 224-20320 and LV4-20320 of Contract No. 68-C5- 0091 between the U.S. Environmental Protection Agency National Environmental Research Laboratory and the Lockheed Martin Services Group, Las Vegas, Nevada. The EPA Work Assignment Manager on this task was Larry A. Eccles. The monitoring records for Nevada heap leaching facilities were obtained from the Bureau of Mining Regulation and Reclamation, Nevada Department of Environmental Protection. The assistance and cooperation of Douglas Zimmerman and Matt McAuliffe in obtaining this information is acknowledged and appreciated. The monitoring records for Arizona copper mining facilities were obtained from the Arizona Department of Environmental Quality.
    [Show full text]
  • Igneous Geology of the Carlin Trend, Nevada: the Importance of Eocene Magmatism in Gold Mineralization
    University of Nevada, Reno Igneous Geology of the Carlin Trend, Nevada: The Importance of Eocene Magmatism in Gold Mineralization A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Geology by Michael Walter Ressel, Jr. Dr. Christopher D. Henry/Dissertation Advisor May, 2005 UMI Number: 3210296 UMI Microform 3210296 Copyright 2006 by ProQuest Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, MI 48106-1346 Copyright ©, 2005 by Michael Walter Ressel, Jr. All Rights Reserved i ABSTRACT Igneous rocks of five ages are present in the Carlin trend, Nevada, and include: 1) Paleozoic basalt of the Roberts Mountains allochthon, 2) the Jurassic (~158 Ma) Goldstrike intrusive complex, which includes the Goldstrike diorite laccolith and abundant dikes and sills, 3) a Cretaceous (112 Ma) granite stock, 4) lavas and intrusions of the Emigrant Pass volcanic field and widespread epizonal plugs and dikes of Eocene (~40-36 Ma) age that range from rhyolite through basalt, and 5) Miocene (15 Ma) rhyolite lava and tuff. Jurassic and Eocene igneous rocks are by far the most important volumetrically and are spatially associated with nearly all ore deposits of the Carlin trend. This study focuses on the field relations, isotopic dating, and geochemistry of Eocene dikes that intrude sedimentary rocks in many deposits of the Carlin trend, because they are the youngest pre-mineral rocks and have simpler alteration histories than other host rocks.
    [Show full text]
  • CPY Document Title
    26 New Data on Minerals. M., 2006. Vol. 41 UDC549.35 NEW DATA ON GALKHAITE Igor V. Pekov, Igor A. Bryzgalov Lomonosov MoscowState University, Department ofMineralogy, Moscow, [email protected] The chemical composition of galkhaite from several deposits (Gal-Khaya, Yakutia, Russia; Khaidarkan, Chauvay, Kyrgyzstan; Getchell, Nevada, U.S.A.) was studied using the electron microprobe. Galkhaite from all these deposits contains species-forming Cs (3.6 - 6.6 wt %) prevailing over thallium (Cs > Tl) in all samples. The miner­ al from Khaidarkan contains up to 1.0 wt. %, from Chauvay - up to 2.9% Ag. Contents of Na, K, Rb, Ca, Sr, Ba, Pb, Cd, Fe, Se, Te in all the studied samples were below detection limits. It is suggested that the empirical formula of galkhaite be calculated on the basis of the sum: (Hg+Cu+Zn+Fe+Ag+As+Sb+S)= 22. The (Cs,Tl) occu­ pancyis 50-100%, and that suggests the refined idealized formula of galkhaite: (Cs,Tl)o.s., (Hg,Cu,Zn)6(As,Sb)4S'2' The influence of conditions of the microprobe analysis on the results for galkhaite and the crystallochemical rea­ son of strong affinity of the mineral to cesium, the indicator role of galkhaite as related to the Cs geochemistry are discussed. The concentration of cesium in the process of formation of hydrothermal arsenic-antimony-mercury mineralization is the main factor limiting the amount of galkhaite crystallized, so that Cs activity may determine the types of mercury ore. 2 tables, 18 references. Galkhaite, (Cs,Tl)(Hg,Cu,Zn)6(As,Sb)4S12' is heavy element surrounded by 12 atoms of sul­ typical mineral of some low-temperature fur, which had not been found by Kaplunnik hydrothermal ore deposits.
    [Show full text]
  • SYMPOSIUM PROGRAM and ABSTRACTS VOLUME April10
    19th International Geochemical Exploration Symposium Exploration Geochemistry into the 21st Century The Association of Exploration Geochemists SYMPOSIUM PROGRAM AND ABSTRACTS VOLUME Vancouver1 British Columbia, Canada April10--16, 1999 Hotel Vancouver THE ASSOCIATION OF EXPLORATION GEOCHEMISTS P.O. Box 26099, Roht.:nson Rd. Nepean, Ontario, K21l 9RO, Canada OFFlCERS President Erick F.Wcihmd AGRA E:H lh and Environmental Secretary David B. Smith U.S.Ccological Survey Treasurer Gwcndy E.M.Hall Geologio1l Survey of Canada COl,~C I LLORS 1997- 1999 Roherr Clark, William B.Coker, John S.Conc, tcphen J. D<ly, Shea Clark Smith, Barry W.Smee 1999- 2000 Duvid Gamen, Eric Hoffm;m, Ray Lett, M.Bcth McClenaghan, J.Thomas Nash Australia Leigh Bertenay, Nigel Radford, Mark Elliott Brasil M.Lima Ja Costa Chile Vacant China Guangshen Yan Ern·ope B\)UJwijn de Smeth Northern Countries Clemen$ Reimann South East Asia T.Nuchangong Southern Africa Chnrles Okujeni U.K. and Ireland C.C.J ~) hnson 19th INTERNATIONAL GEOCHEMICAL EXPLORATlON SYMPOSIUM ORGANISING COMMITTEE Chairman Barry W. Smee, Smee anJ Associates Consulting Ltd. Co-Treasurer Giles R. PeatfielJ, Consulring GeologisT Co-Treasurer Ray Lett, B.C. Geological Survey Co-Secretary Bruce W. D(lwning. Gamah International Ct)-Secretary lvor L. Elliott, Geochernist Technical Program W.K. Fle1cher, U niversity of British Cl)lumhia lmr L. Elliott, Geochemist Short Courses Steve Cook, B.C.Geological Survey John B<)rakso, Consultant Field Trips Bruce Ball;mtyne, Consulting Geoll,gisr DaviJ VanJerklcy, C1minco LrJ Trade Show Jnhn Gravel, Acme Analytica l Lahorarorics LrJ Bruce W. Downing, Gamah International Social Program Kathy Laurus, Consulting Geologist Patricia Murphy, Venue West Conference Services Ltd Publicity David Smid1, T.S.L.
    [Show full text]